test script for generating thumbnails in an electron app

thumbnails.js

//updated to save thumbnails!

var h = require('hyperscript')
var fs = require('fs')
var pull = require('pull-stream')
var paramap = require('pull-paramap')
var path = require('path')

//XXX note, I added `module.exports = downsample` to the bottom of this file, TODO: make PR
var downsample = require('downscale/src/downsample')

var dir = process.argv[2], pool = []
fs.readdir(dir, function (err, ls) {
  var canvas = document.createElement('canvas')
  var canvas2 = document.createElement('canvas')
  canvas.width = 50
  canvas.height = 50
  var ctx = canvas.getContext('2d')
  var start = Date.now()
  document.head.appendChild(h('style', {textContent: 'body { margin: 0px; line-height: 0px; }'}))
  var content = h('div')
  var perf = h('h1'), size = 0, size2 = 0
  document.body.appendChild(h('div', perf, content))
  try {
  fs.mkdirSync(path.join(dir, '.thumbnails'))
  } catch (_) {}
  pull(
    pull.values(ls),
    paramap(function (file, cb) {
      var base = path.basename(file)
      var thumbnail = path.join(dir,'.thumbnails', file)
      fs.stat(thumbnail, function (err, stat) {
        if(err) return cb(null, file)
        else return cb(null, thumbnail)
      })
    }),
    paramap(function (file, cb) {
      if(/.thumbnail/.test(file)) return cb(null, h('img', {src: file}))

      var img = pool.length ? pool.shift() : h('img')
      img.src = path.resolve(dir, file)
      img.onload = function (ev) {
        var size = Math.min(img.width, img.height)
        size2 += img.width * img.height
        if(true) {
          ctx.drawImage(img, (img.width - size)/2, (img.height - size)/2, size, size, 0, 0, canvas.width, canvas.height)
        } else {
          //
          canvas2.width = size
          canvas2.height = size
          var ctx2 = canvas2.getContext('2d') 
          ctx2.drawImage(img, (img.width - size)/2, (img.height - size)/2, size, size, 0, 0, size, size)
          ctx.putImageData(downsample(ctx2.getImageData(0,0,size,size), canvas.width, canvas.height, 0, 0, size, size), 0, 0)
        }
        img.onerror = img.onload = null
        pool.push(img)
        var data = canvas.toDataURL('image/jpg')
        data = data.substring(data.indexOf(',')+1)
        var thumbnail = path.join(dir, '.thumbnails', file)
        fs.writeFile(thumbnail, new Buffer(data, 'base64'), function (err) {
          cb(null, h('img', {src:  thumbnail}))
        })
      }
      img.onerror = function (ev) {
        cb(null)
      }
    }, 32, false),
    pull.filter(),
    pull.drain(function (img) {
      content.appendChild(img)
      var count = content.children.length
      var time = (Date.now()-start)/1000
      size += (Math.round(img.src.length/1000))/1000
      perf.textContent = [count, size.toString().substring(0, 5), ((Math.round(size2/1000))/1000).toString().substring(0, 5), time, count/time].join(', ')
    }, function (err) {
      if(err) throw err
    })
  )
})